from app import db, login_manager
from flask_login import UserMixin
from datetime import datetime

@login_manager.user_loader
def load_user(user_id):
    return User.query.get(int(user_id))

class User(db.Model, UserMixin):
    id = db.Column(db.Integer, primary_key=True)
    username = db.Column(db.String(20), unique=True, nullable=False)
    email = db.Column(db.String(120), unique=True, nullable=False)
    password = db.Column(db.String(60), nullable=False)
    role = db.Column(db.String(20), default='user')
    created_at = db.Column(db.DateTime, default=datetime.utcnow)

    def __repr__(self):
        return f"<User {self.username}>"

class Major(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    name = db.Column(db.String(50), unique=True, nullable=False)
    students = db.relationship('Student', backref='major', lazy=True)

    def __repr__(self):
        return f"<Major {self.name}>"

class Student(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    student_id = db.Column(db.String(20), unique=True, nullable=False)
    name = db.Column(db.String(50), nullable=False)
    gender = db.Column(db.String(10), nullable=False)
    age = db.Column(db.Integer, nullable=False)
    major_id = db.Column(db.Integer, db.ForeignKey('major.id'), nullable=False)
    created_at = db.Column(db.DateTime, default=datetime.utcnow)

    def __repr__(self):
        return f"<Student {self.name}, ID: {self.student_id}>"